1. Field of the Invention
The present invention relates to a semiconductor device and a fabricating method thereof, and in particular, to a static random access memory (SRAM) and a fabricating method thereof.
2. Description of Related Art
Random access memory devices can be mainly classified into dynamic random access memories (DRAMs) and static random access memories (SRAMs). The SRAMs are advantageous in high speed operation and lower power consumption. Moreover, compared with the DRAMs, the SRAMs need not to be re-charged periodically, so the design and the fabrication thereof are simplified. Hence, the SRAMs are widely employed in information electronic products.
Generally, a memory cell of the SRAM includes two drive transistors, two load devices and two access transistors. The load devices can be resistors or transistors. Therefore, according to the types of the load devices, the SRAM can be classified into a 4T2R SRAM formed by 4 transistors and 2 resistors, and a 6T SRAM formed by 6 transistors. The 4T2R SRAM can be, for example, a high load resistor SRAM (HLR SRAM). The 6T SRAM can be, for example, a full complementary metal-oxide-semiconductor SRAM (Full CMOS SRAM) or a thin film transistor SRAM (TFT SRAM). In terms of the requirement of fabricating the SRAM having low power and a low voltage, the SRAM having a memory cell formed by 6 transistors (6T) has higher stability.
Generally, in order to reduce the resistance of the SRAM and promote the operating speed of the SRAM, the salicide is formed on the gate of the transistor and on the active region of the silicon substrate in the SRAM. Although the salicide has the aforesaid advantages, a current leakage problem might occur due to a spiking effect caused by the salicide formed on the active region. Under the circumstance that a space of the active region is larger, the current leakage problem caused by the spiking effect is slight and even can be ignored. However, as the size of the devices are continuously miniaturized and the level of the integration of the devices increases accordingly, when the space in the active region is narrowed to some extent, the current leakage problem caused by the spiking effect can no longer be ignored.